1. Field of the Invention
The present invention relates to a system, method, and computer program for verifying data recorded on an information recording medium. More particularly, the invention relates to a system, method, and computer program for verifying information with reliability while retaining a high level of security, the information including content to be copyright-protected and a cipher key, which are stored in an information recording medium and have to be prevented from being leaked.
2. Description of the Related Art
Software data (hereinafter, referred to as content), e.g., audio data such as a music track, image data such as a movie, a game program, or an application program can be stored as digital data in a recording medium such as a Blu-ray Disc using a blue laser, a digital versatile disc (DVD), a Mini-Disc (MD), or a compact disc (CD). In particular, a Blu-ray Disc is capable of recording at high density. Large-capacity video content can be recorded as high-quality data on a Blu-ray Disc.
Digital content stored in various information recording media are distributed to users. The user uses a personal computer (PC) or a playback unit such as a disc player to play back or use the content.
In general, the rights of many pieces of content, such as music data items and image data items, are possessed by their authors or distributors, respectively. In distributing content, usually, the use of the content is restricted, i.e., permission for the use thereof is given to only authorized users so as to prevent unauthorized copying.
In digital recording apparatuses and recording media, data such as image data and audio data can be repeatedly recorded and reproduced without being deteriorated. Unfortunately, the following problems often occur: Unauthorized copies of content are distributed over the Internet; CD-Rs including unauthorized copies of content, i.e., pirated discs, are distributed; and content is stored in hard disks of PCs of unauthorized users without permission, and the copied content is illegally used.
DVDs and large-capacity recording media using blue lasers, which are being developed, are capable of storing a large amount of data corresponding to one or more movies as digital information. As it becomes possible to record image information as digital information, the challenge to prevent unauthorized copying to protect copyright holders becomes more important. To prevent unauthorized copying of digital data, various technologies for preventing illegal copying are in practical use in digital recording apparatuses and recording media.
In manufacturing information recording media, such as CDs or DVDs, each storing content, a plurality of entities, such as a content owner, a content editor, a disc manufacturer, and a key management center (Key Issuing Center: KIC) for managing and issuing keys for encryption, provide necessary information, and the information is distributed and verified between the entities to produce recording information media.
For instance, a disc producing entity serving as a disc production plant verifies data provided by the content editor to execute a process of recording data on each disc. In addition, the disc producing entity performs a verification process of checking whether data recorded on each disc matches the data to be recorded. This process is executed based on a checking process of comparing data reproduced from each recorded disc with the data to be recorded. In the above-mentioned data verification process, reproduced data to be verified may be leaked. If data leakage occurs, the profits of the content right holder may be lost.
Typical disc production and data verification will now be described with reference to FIG. 1. FIG. 1 shows a key management center (Key Issuing Center: KIC) 101 for executing a process of managing and issuing keys, a content editing entity 102, such as a studio, for executing a content editing process, and a recording medium producing entity 110 serving as a disc production plant. The recording medium producing entity 110 receives a cipher key issued by the key management center 101 and cipher-key related information, such as key generation information, from the key management center 101. In addition, the recording medium producing entity 110 receives edited content to be recorded on a disc and content-related information from the content editing entity 102.
In the recording medium producing entity 110, a data generation unit (Formatter) 111 executes a process of recording the cipher key and the cipher-key related information received from the key management center 101 and the edited content received from the content editing entity 102 on an information recording medium (Disc) 112 in a predetermined format. At that time, as necessary, the data generation unit 111 executes a process of encrypting the content using the cipher key received from the key management center 101 and records encrypted data on the information recording medium 112.
The content and various cipher key information items are recorded on each information recording medium. Subsequently, the recording medium producing entity 110 executes a verification process of checking whether data recorded on the information recording medium 112 is valid. All recorded discs or sampled discs are subjected to the verification process.
The verification process is performed such that data reproduced by a data reproduction unit (Drive) 113 and data output by the data generation unit 111, i.e., two data streams, are supplied to a recording medium verification unit 114 (Disc Checker) 114 to compare the two data streams.
In executing the verification process, content data and cipher key information, which have to be prevented from being leaked, are transferred as data to be compared in a data path between the data generation unit 111 and the recording medium verification unit 114 and that between the data reproduction unit 113 and the recording medium verification unit 114. If data is leaked from any data path by interception, the profits of the content right holder may be lost.